In the web offset printing process, a continuous web of paper is transported through a printing press. Near the beginning of the press, one or more printing units apply ink to the web to repeatedly create a pattern, or impression, of text and images. At the end of the press, a web conversion machine, such as a folder, is typically used to cut and fold the web into signatures.
There are many known ways to convert a web into signatures. The web is commonly slit into ribbons, which can be stacked on top of each other and then former folded. Some folders, such as pinless former folders, cut the ribbons or web and deliver one or more streams of signatures. Other folders, such as combination folders, commonly introduce additional folds, such as half-folds and quarter-folds.
A common method of creating a quarter fold uses a chopper module. A chopper module has a blade that forces signatures through a nip formed by two rotating rollers. The signature is folded as it passes through the nip.
As shown in FIG. 1, due to limitations on space between consecutive signatures, paper dynamics, and mechanical component strength, a high speed folder 10 typically has two chopper modules 12, 14, each folding every other signature. Using two chopper modules 12, 14 allows both chopper modules 12, 14 to run at roughly half the speed of the printing press, making it possible to produce high quality quarter folded products. Chopper modules 12, 14 are expensive from both a cost and space standpoint.